Case 1
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
Good Practices
Design
Pipe failure is a cumulative effect of various pipe-intrinsic (material, diameter, age), operational (corrosion,
pressure) and environmental factors (rainfall, soil conditions and external stresses) acting on them. Factors attributed to pipe failure can also be classified into hydraulic or non-hydraulic factors. Specify materials that are resistant to corrosion and non-reactive to the conveyed water and surrounding ground in accordance with BS EN 545, BS EN 598 or equivalent, and that do not impart any taste or toxicity to the water in accordance with SS 375-1 or equivalent.
Use of a single material for the entire system is preferable for easy connection/jointing. Specify pipe system material that does not react with the pumped medium. The top 3 water pipe materials
are: (1) Copper — durable; with antibacterial properties; good conductor of heat and hence ideal as
hot water pipes, (2) Stainless Steel — durable; resistant to corrosion; non-toxic; ideal as drinking
water pipes, and (3) Plastic (UPVC, PPR, PVC, PE, PP) — durable; resistant to corrosion and chemical.
Construction
Since the 1980s, PUB has systematically replaced older, unlined iron pipes with cement-lined ductile iron and steel pipes. In addition, the exterior of these pipes is coated with bitumen. With the pipes’ interiors lined with cement, the metal is shielded and thus reduces the occurrence of internal corrosion. The fibreglass wraps are applied to the pipe enamel to produce a more uniform coating, allow a thicker application of enamel, and enhance the coating strength. The bitumen coating with two layers of fibreglass protects the external surface of the pipe from corrosion. Pipe penetrations and joints should strictly adopt the manufacturer’s instructions. Jointing material should not enter the pipe. Caulking at the penetration sleeve should be made watertight. Proper installation should be fulfilled while ensuring that the protective coating is not lost/damaged during installation in accordance with BS 8558, SS 636 or equivalent. Non-metallic fittings shall comply with SS 375 or BS 6920. Metallic fittings shall comply with AS/NZS 4020.